How to get citizenship for child under 18 with ILR but was born outside UK

[jb51214]

Background:
1. We are family of 5. Husband, Wife, eldest child born in 2009 before we came to UK, and two younger children born in UK, before we got ILR.
2. We got our ILRs last year (Husband, Wife, Eldest Child)
3. After that younger two children were 'registered' for citizenship and got the passports.

We are looking to apply for Citizenship in coming week.
Q1. "Application for citizenship" has eligibility criteria of age > 18 years.
A) How do I register/apply for eldest child (aged 12 - her ILR stay is now 12 months already)?
B) Which form to fill? As she was born outside UK when none of the parents had ILR, do we still need to apply using MN1 route? Section 3(1)?

Q2. I presume we can all travel outside UK in July/August, after applying and use out BRPs to re-enter UK. Is that correct?

Q3. Do I get "Citizen Certificate" after the Ceremony? i.e. before the ceremony, ILR will be valid?

Regards

[secret.simon]

You use the same form (Form MN1) as for your youngest two children.

B) Which form to fill? As she was born outside UK when none of the parents had ILR, do we still need to apply using MN1 route? Section 3(1)?

Yes to both the last two questions.